1. Field of the Invention
This invention relates to a gauge for ascertaining the axial position of the edge of the rim of a wheel mounted on a wheel balancer.
2. Description of the Prior Art
Exemplifying the prior art environment in which the present invention can be employed is U.S. Pat. No. 3,636,733. The U.S. Pat. No. 3,636,773 patent discloses a wheel balancing apparatus wherein the distance to the planes of the inner and outer edges of a wheel rim are ascertained with respect to some reference point or points within the apparatus. Location of the planes in which the inner and outer rim edges reside is essential because it is at such location that weights are installed to balance the wheel/tire assembly. The mechanism disclosed in the U.S. Pat. No. 3,636,773 patent is adapted to move the wheel/tire assembly longitudinally of the shaft on which it is mounted until the plane of the inner rim edge is disposed in a prescribed axial position. Although the U.S. Pat. No. 3,636,733 apparatus provides acceptable results, the mechanism needed to achieve such results is unduly complicated because of the necessity that the wheel/tire assembly move longitudinally of the drive shaft on which it is mounted.
U.S. Pat. No. 3,910,121 discloses a wheel balancing machine which has an arm disposed outward of the periphery of the tire. There are two clamping assemblies adapted to slide along the arm so that the clamping assemblies can be visually positioned in alignment with the planes of the inner and outer edges of the wheel rim. Although the apparatus disclosed in the U.S. Pat. No. 3,910,121 patent produces satisfactory results, the accuracy depends in large part on the judgment of the operator because visual alignment between the clamping assembly and the wheel rim extremities is obstructed by the tire.
Another prior art mechanism for measuring the position of the plane of the inner wheel rim edge includes an elongate rigid rod supported for movement in a direction parallel to the shaft on which the wheel/tire combination is mounted. The rod has graduations thereon so that when the outer end of the rod is moved into alignment or into contact with the inner rim edge, the distance to that edge can be ascertained by noting the relative position of the graduations to a fixed index mark. This prior art arrangement also gives satisfactory results but is unduly complicated and expensive, and is dangerous in that if the rod is not retracted before power is applied to the wheel, the rod and/or the wheel can be damaged should they contact one another while the wheel is rotating.